casual observance of most situations, rules that are not absolutes that are superceded under unique circumstances such as creating the One Ring or presenting an ultimatum under parely to your main remaining foes that you are about to crush or enslave.

On a different tack, there were comments above about the Nazgul as willing servants of Sauron....this is the opposite to the real situation. They were utterly enslaved through their rings, which Sauron has in his possesion. As mortal men they willingly accepted the rings but they had no idea of the ultimate consequence.